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(significant_bits, num_sign_bit_copies): Handle SUBREGs made for promoted

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variables.

From-SVN: r2215
This commit is contained in:
Richard Kenner 1992-09-23 19:23:19 -04:00
parent d6749decf6
commit c3c2cb3741
1 changed files with 16 additions and 0 deletions
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16
gcc/combine.c
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@ -6083,6 +6083,14 @@ significant_bits (x, mode)
break;
case SUBREG:
/* If this is a SUBREG formed for a promoted variable that has
been zero-extended, we know that at least the high-order bits
are zero, though others might be too. */
if (SUBREG_PROMOTED_VAR_P (x) && SUBREG_PROMOTED_UNSIGNED_P (x))
significant = (GET_MODE_MASK (GET_MODE (x))
& significant_bits (SUBREG_REG (x), GET_MODE (x)));
/* If the inner mode is a single word for both the host and target
machines, we can compute this from which bits of the inner
object are known significant. */
@ -6220,6 +6228,14 @@ num_sign_bit_copies (x, mode)
return (sig == 0 ? bitwidth : bitwidth - floor_log2 (sig) - 1);
case SUBREG:
/* If this is a SUBREG for a promoted object that is sign-extended
and we are looking at it in a wider mode, we know that at least the
high-order bits are known to be sign bit copies. */
if (SUBREG_PROMOTED_VAR_P (x) && ! SUBREG_PROMOTED_UNSIGNED_P (x))
return (GET_MODE_BITSIZE (mode) - GET_MODE_BITSIZE (GET_MODE (x))
+ num_sign_bit_copies (SUBREG_REG (x), GET_MODE (x)));
/* For a smaller object, just ignore the high bits. */
if (bitwidth <= GET_MODE_BITSIZE (GET_MODE (SUBREG_REG (x))))
{